A selective two-step doping method was developed to prepare metallic Ti-doped NaAlH₄ in which a catalytic amount of metallic Ti was first milled with NaH and then milled again after adding Al powder (NaH:Al=1: 1). As determined by the combined X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM) examinations, the utilization of this novel doping method has produced a more homogeneous dispersion of the fine Ti hydride particles in the NaH/Al matrix, compared to the sample prepared by the traditional one-step milling. As a result, both the hydrogen capacity and de-/hydriding kinetics of the doped materials have been markedly improved. For the NaH + Al + 0.04Ti mixture mechanically milled for 20 h, the cycling hydrogen capacity of the two-step milled sample reached to over 4.3 wt %, about 40% higher than the sample prepared by the traditional one-step method. Moreover, it was observed that the cycling performance of the doped material was highly stable over several hydriding/dehydriding cycles. On the basis of these results, a discussion regarding the nature of catalytically active species was given.

Xiang Dong Kang;Ping Wang;会明 成

Journal of Physical Chemistry C

2007-3-29

SnO ₂ quantum dots (QDs) ended with chlorine ions are introduced at the interface of spin-coated TiO ₂ electron selective layer (ESL)/perovskite to fill the pinholes in the layer and passivate the trapping defects. As a result of the increased interface electron collection and reduced bulk recombination, the planar perovskite solar cell with the QDs modified ESL gives the large power conversion efficiency enhancement from 14.9% to 17.3% and greatly improved stability under the continuous light irradiation.

Tingting Wu;Chao Zhen;Jinbo Wu;Chunxu Jia;Mustafa Haider;Lianzhou Wang;Gang Liu;会明 成

Science Bulletin

2019-4-30

Carbon nanotube (CNT)/high-density polyethylene (HDPE) composites with different CNT fractions were prepared by melting the blend, and the mechanical properties and crystallization of the CNT/HDPE composites obtained were investigated. It was found that the tensile modulus of the CNT/HDPE composites with 2 w/%, 5 w/% and 10 w/% CNTs are increased by 7.4%, 27.0% and 28.6%, respectively, and the yield strength is increased by 3.3%, 14.4% and 18.5%, respectively, but their strength and elongation at fracture are decreased. The differential scanning calorimetry (DSC) results show that the onset temperature of crystallization (T₀) of HDPE is increased and the activation energy of crystallization is decreased due to the presence of CNTs, but its crystallization rate and crystallinity are decreased due to the hindering of the movement of the HDPE molecular chains by CNTs during crystallization.

Xin Tong;Xiu Juan He;会明 成

Xinxing Tan Cailiao/New Carbon Materials

2004-12

会明 成

Wuli Huaxue Xuebao/ Acta Physico - Chimica Sinica

2019

The structures of two types of mesophase pitch-based carbon fibers (M30 and M70) reinforced SiC composites, prepared by the polycarbosilane impregnation-pyrolysis process, were investigated using transmission electron microscopy (TEM). It was found that M70 possessed a highly-ordered graphite structure despite occasional misorientation of some crystallites. However, the skin of M70 was less ordered than the interior of M70. The structure of M30 was uniform throughout, and was less ordered than that of M70. The fiber and matrix in M70/SiC bonded weakly, whereas the fiber and matrix in M30/SiC bonded tightly and locked together. This difference in the interface feature originates from the difference of the surface crystalline structures of M30 and M70, and is formed during the first impregnation-pyrolysis cycle of polycarbosilane.

Guobin Zheng;Hideaki Sano;Kunio Suzuki;Kazuo Kobayashi;Yasuo Uchiyama;会明 成

Carbon

1999

Substitutional doping provides an effective strategy to tailor the properties of 2D materials, but it remains an open challenge to achieve tunable uniform doping, especially at high doping level. Here, uniform lattice substitution of a 2D Mo₂C superconductor by magnetic Cr atoms with controlled concentration up to ≈46.9 at% by chemical vapor deposition and a specifically designed Cu/Cr/Mo trilayer growth substrate is reported. The concentration of Cr atoms can be easily tuned by simply changing the thickness of the Cr layer, and the samples retain the original structure of 2D Mo₂C even at a very high Cr concentration. The controlled uniform Cr doping enables the tuning of the competition of the 2D superconductor and the Kondo effect across the whole sample. Transport measurements show that with increasing Cr concentration, the superconductivity of the 2D Cr-doped Mo₂C crystals disappears along with the emergence of the Kondo effect, and the Kondo temperature increases monotonously. Using scanning tunneling microscopy/spectroscopy, the mechanism of the doping level effect on the interplay and evolution between superconductivity and the Kondo effect is revealed. This work paves a new way for the synthesis of 2D materials with widely tunable doping levels, and provides new understandings on the interplay between superconductivity and magnetism in the 2D limit.

Chuan Xu;Zhen Liu;Zongyuan Zhang;Zhibo Liu;Jingyin Li;Minghu Pan;Ning Kang;会明 成;Wencai Ren

Advanced Materials

2020-9-1

Tetrapod-like zinc oxide materials with nanorod-nanowire structure were prepared. SEM, TEM and XRD investigations showed that the tetrapod-like ZnO materials had a hexagonal wurtzite crystal structure. The length of each leg is 1-2 μm, the diameter of nanorods is 100-200 nm and the diameter of nanowires is about 30 nm in a single tetrapod-like ZnO rod-wire nanostructure. The formation of this nanostructure was interpreted by a vapor-solid (VS) mechanism. The photoluminescence of ZnO nanomaterial under laser radiation at room temperature was further investigated. Their ultra-violet emission (wavelength is ∼380 nm) and green emission (wavelength is ∼520 nm) mechanism was discussed.

Anze Ni;Hongtao Cong;会明 成

Cailiao Yanjiu Xuebao/Chinese Journal of Materials Research

2005-4

A variety of carbon nano- and submicro-structures with spectacular morphologies such as spaghetti-like, dendritic, and segmented carbon fibers; carbon pillars; and single-walled carbon nanotubes (SWNTs) was selectively synthesized by the alcohol chemical vapor deposition (CVD) method. The phase structure and morphologies were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and Raman spectroscopy. The carbon structures could be controlled by adjusting the deposition position and the growth temperature. The formation mechanism of these carbon structures was discussed on the basis of the experimental results. The various CVD products obviously imply that the growth mechanism for our alcohol CVD process evolves from catalytic growth mode to pyrolytic carbon deposition mode. The obtained various carbon nano- and submicro-structures may be promising for applications in functional nanodevices.

Z. G. Zhao;S. Bai;Z. Ying;Jin Bo Bai;会明 成

Journal of Materials Research

2006-10

X-ray diffraction (XRD) analysis revealed that nanocrystalline Ti hydride(s) was in situ formed during mechanical milling 1:1 NaH/Al mixture with metallic Ti powder. The composition of the formed Ti hydrides varies slightly upon changing the milling atmosphere from inert Ar to reactive H₂. Directly doping sodium alanate with commercial Ti hydride was found to result in similar dehydriding kinetics, hydrogen capacity, and cycling stability to those of the samples doped with metallic Ti. Moreover, according to the XRD results, the Ti hydride(s) remains stable in the de-/hydrogenation cycles. On the basis of these results, a discussion regarding the nature of catalytically active species was given.

X. D. Kang;P. Wang;会明 成

International Journal of Hydrogen Energy

2007-9

We report tunable band gaps and transport properties of B-doped graphenes that were achieved via controllable doping through reaction with the ion atmosphere of trimethylboron decomposed by microwave plasma. Both electron energy loss spectroscopy and X-ray photoemission spectroscopy analyses of the graphene reacted with ion atmosphere showed that B atoms are substitutionally incorporated into graphenes without segregation of B domains. The B content was adjusted over a range of 0-13.85 atom % by controlling the ion reaction time, from which the doping effects on transport properties were quantitatively evaluated. Electrical measurements from graphene field-effect transistors show that the B-doped graphenes have a distinct p-type conductivity with a current on/off ratio higher than 10 ². Especially, the band gap of graphenes is tuned from 0 to ∼0.54 eV with increasing B content, leading to a series of modulated transport properties. We believe the controllable doping for graphenes with predictable transport properties may pave a way for the development of graphene-based devices.

Yong Bing Tang;Li Chang Yin;Yang Yang;Xiang Hui Bo;Yu Lin Cao;Hong En Wang;Wen Jun Zhang;Igor Bello;Shuit Tong Lee;会明 成;Chun Sing Lee

ACS Nano

2012-3-27